Field of the Invention
The present invention relates to polypeptides having mannanase activity, catalytic domains, and carbohydrate binding modules, and polynucleotides encoding the polypeptides, catalytic domains, and carbohydrate binding modules. The invention also relates to nucleic acid constructs, vectors, and host cells comprising the polynucleotides as well as methods of producing and using the polypeptides, catalytic domains, and carbohydrate binding modules.
Description of the Related Art
Mannans are a type of hemicellulose representing up to 25% of wood dry weight in softwoods, but are also found in other plant material, especially in a variety of seeds. Mannans are polysaccharides with a backbone of β-1,4-linked D-mannopyranosyl residues, which can contain galactose or acetyl substitutions and may have glucose residues in the backbone. The main enzyme type participating in the degradation of mannans are endo-1,4-β-mannanases (EC 3.2.1.78), which hydrolyze the internal glycoside bonds in the mannan backbone.
Thus it could be advantageous to use endomannanases in applications where mannan needs to be degraded. Examples of where mannanases could be used are in the production of bioethanol from softwood (Várnai et al, (2011) “Synergistic action of xylanase and mannanase improves the total hydrolysis of softwood”, Bioresource tech., 102(19), pp. 9096-104) and palm kernel press cake (Jørgensen et al, (2010) “Production of ethanol and feed by high dry matter hydrolysis and fermentation of palm kernel press cake”, Applied Biochem. Biotech., 161(1-8), pp. 318-32), for the improvement of animal feed (Cai, et al, (2011), “Acidic β-mannanase from Penicillium pinophilum C1: Cloning, characterization and assessment of its potential for animal feed application”, J. Biosci. Bioeng., 112(6), pp. 551-557) and in the hydrolysis of coffee extract (Nunes et al, (2006), “Characterization of Galactomannan Derivatives in Roasted Coffee Beverages”, J. Agricultural Food Chem., 54(9), pp. 3428-3439). Furthermore, guar gum is used in many food products, and so mannanases could be used in detergents to remove mannan containing stains.
According to CAZy (www.cazy.org), endo-1,4-β-mannanases can be found in glycoside hydrolyase families 5, 26 and 113. Couturier et al. have reported a GH26 mannanase from Podospora anserina having 56.1% and 76.4% identity to SEQ ID NO: 3 and 6 respectively in (2013), “Structural and Biochemical Analyses of Glycoside Hydrolase Families 5 and 26-(1,4)-Mannanases from Podospora anserina Reveal Differences upon Manno-oligosaccharide Catalysis”, J. Biol. Chem., 288(20): 14624-14635.
However, there are currently no reports in the literature describing that GH26 mannanases can be used for degrading highly substituted mannan. Furthermore, there are very few examples of fungal GH26 mannanases. The present invention provides polypeptides having mannanase activity and polynucleotides encoding the polypeptides that are highly active in degrading different types of mannan, and therefore could be used in the aforementioned applications.